The present invention relates to novel polymers. The present invention also relates to metal-ligand complexes, catalysts and catalyst compositions that are active for polymerizing olefins. The invention also relates to certain of these catalysts and catalyst compositions that polymerize ethylene and styrene to a product having unique properties.
Ancillary (or spectator) ligand-metal coordination complexes (e.g., organometallic complexes) and compositions are useful as catalysts, additives, stoichiometric reagents, monomers, solid-state precursors, therapeutic reagents and drugs. Ancillary ligand-metal coordination complexes of this type can be prepared by combining an ancillary ligand with a suitable metal compound or metal precursor in a suitable solvent at a suitable temperature. The ancillary ligand contains functional groups that bind to the metal center(s), remain associated with the metal center(s), and therefore provide an opportunity to modify the steric, electronic and chemical properties of the active metal center(s) of the complex.
One example of the use of these types of ancillary ligand-metal complexes and compositions is in the field of polymerization catalysis. In connection with single site catalysis, the ancillary ligand typically offers opportunities to modify the electronic and/or steric environment surrounding an active metal center. This allows the ancillary ligand to assist in the creation of possibly different polymers. Group 4 metallocene based single site catalysts are generally known for polymerization reactions. See, generally, xe2x80x9cChemistry of Cationic Dicyclopentadienyl Group 4 Metal-Alkyl Complexesxe2x80x9d, Jordan, Adv. Organometallic Chem., 1991, Vol. 32, pp. 325-387 and xe2x80x9cStereospecific Olefin Polymerization with Chiral Metallocene Catalystsxe2x80x9d, Brintzinger, et al., Angew. Chem. Int. Ed. Engl., 1995, Vol. 34, pp. 1143-1170, and the references therein, all of which is incorporated herein by reference.
One application for metallocene catalysts is producing ethylene copolymers. For example, PCT Application WO 00/37512 and published U.S. patent application publication No. US 2001/0031843 A1 employ reaction product of zirconium tetrabenzyl and two equivalents of a phenol-triazole ligand with MMAO activation as catalyst for ethylene-hexene copolymerization (see Example 3). This application reports production of solid polyethylene, and states that the catalysts described are expected to produce HDPE (i.e., ethylene homopolymer) under ethylene-hexene copolymerization conditions (i.e., no incorporation of hexene).
As generally known to those of skill in the art of olefin polymerization, styrene is generally a more difficult comonomer to incorporate into an ethylene-xcex1-olefin copolymer during copolymerization as compared with 1-hexene or 1-octene. See, e.g., Carlini et al., polymer 42 (2001) 5069-5078 (xe2x80x9cThe copolymerization of styrene with xcex1-olefins by conventional Ziegler-Natta catalysts has been reported to occur with severe limitations.xe2x80x9d) Moreover, most known ethylene styrene copolymers are directed toward polymers where the styrene is present in a chain terminating position (see, e.g., U.S. Pat. Nos. 3,390,141 and 5,180,872 and Pellecchia et al., Marcomolecules, 2000, 33, 2807-2814 and EP 0 526 943). There remains a need to find new ethylene-styrene copolymers and catalysts for such copolymers. In addition there remains a need for new polyolefin catalysts, in general.
Given the state of the art, it was not expected to find a lower molecular weight ethylene-styrene copolymer with unique properties, preferably made during a bulk polymerization process using catalysts formed from phenol-triazole complexes of group 4 metals. It was surprising that such catalysts would incorporate styrene into an ethylene styrene copolymer as well as was found. This invention thus satisfies this desire for the production of ethylene styrene copolymers, particularly in a bulk solution process. Many of the phenol-triazole based catalysts disclosed herein demonstrate high activity for ethylene-styrene copolymerization. These catalysts typically produce low molecular weight ethylene-styrene copolymers with styrene incorporated in the main chain of the polymer, which has a vinyl end group. These lower molecular weight copolymers represent a new and useful class of ethylene-styrene copolymers and may be generally described as liner xcex1-olefins with phenyl substituents placed essentially randomly along the linear chain.
This invention discloses a new class of low molecular weight copolymers having unique bulk properties. This invention also discloses a novel polymerization process for the production of low molecular weight ethylene-styrene copolymers, as well as a novel class of catalysts and ligands making such catalysts. In some embodiments, the catalysts and ligands may be useful for polymerizing a wide variety of polymerizable monomers.
In some embodiments the polymers of this invention may be characterized by either of the general formulas I or II: 
wherein h, i and j are each an integer greater than or equal to 1. The bulk polymers of this invention have a relatively low molecular weight, a relatively narrow molecular weight distribution and an end analysis by NMR that shows a close association between the numbers of vinyl and methyl end-groups. The bulk polymers also show that the styrene monomer incorporated into the chain is typically not at one of the ends of the polymer, but are randomly distributed along the polymer backbone.
Other aspects of this invention include a method of polymerizing ethylene and styrene to form a copolymer using a catalyst. The catalysts of this invention generally comprise a composition or metal-ligand complex, with the ligand employed either being a phenol with a triazole or similar substituent ortho to the hydroxy. In those embodiments where a composition is employed, the ligands are combined with a metal precursor compound at a desired molar ratio (such as 2:1), with the metal precursor comprising a group 4 metal (i.e., zirconium, hafnium or titanium). In those embodiments where a metal-ligand complex is used, the complex may be isolated or formed in situ. The catalyst typically includes an activator, combination of activators or activating technique. The ligands useful in this invention can be generally described by the general formula: 
wherein X1 and X2 are N, and X3, X4, and X5 are independently selected from the group consisting of N and CR15, where R15 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, aryloxy, halo, silyl, boryl, phosphino, amino, thio, seleno, and combinations thereof, provided that at least one and not more than two of X3, X4, and X5 are N; optionally, X3 and X4 may be joined to form a fused ring system having up to 50 atoms, not counting hydrogen atoms; and R1, R2, R3 and R4 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heteroalkyl, substituted heteroalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, aryloxy, halo, silyl, boryl, phosphino, amino, thio, seleno, nitro, and combinations thereof, with the exception that R1 may not be hydrogen, and optionally two or more of R1, R2, R3 and R4 (for example R1 and R2, or R2 and R3, or R3 and R4) may be joined to form a fused ring system having up to 50 atoms, not counting hydrogen atoms.
In other aspects of this invention, certain of the ligands and certain of the metal-ligand complexes are novel. These novel ligands and/or metal complexes can form catalysts useful for the polymerization of a variety of monomers, including xcex1-olefins in general.
Further aspects and objects of this invention will be evident to those of skill in the art upon review of this specification.